VERTICAL OZONE DISTRIBUTION OVER SOUTHERN AFRICA AND ADJACENT OCEANS DURING SAFARI-92

A set of four ozonesonde stations located at Ascension Island, Brazzav ille, Okaukuejo, and Irene, operational during the TRACE A and SAFARI- 92 experiments has provided an opportunity to investigate the vertical distribution of ozone over southern Africa and adjacent oceans. All s tations display a springtime maximum in tropospheric ozone. Enhanced t ropospheric ozone, which occurs between June and September at Brazzavi lle and between July and October at Ascension Island, is linked to dry season biomass burning. The influence of tropical biomass burning is delayed until September at Okaukuejo when a sharp increase in troposph eric ozone is experienced. The biomass burning influence at Irene is l ess because of its more southerly location. A general tropospheric enh ancement is observed at all stations. It is manifest as an enriched la yer in the upper troposphere at Okaukuejo (9-12 km) and Brazzaville (1 1-14 km) and in the lower troposphere (2-8 km) at Ascension Island. At Ascension Island lower tropospheric ozone values are about 20 parts p er billion by volume greater than elsewhere and the tropospheric compo nent here accounts for about 18% of the total column ozone. A series o f tethersonde soundings conducted at hourly intervals at Okaukuejo rev ealed ozone to be well mixed in the lower boundary layer during the da y, but to display marked vertical stratification at night.